This is unfortunate but all too common. I just had a job that was an office building for 30 years (has a DMC, MR interior of building on second floor) that the owner just made into apartments. He called us saying there was something wrong with the elevator, it's too loud. Nope, the elevator was perfectly normal it just was never noticed in an office setting and now that it was apartments it was being complained about, and rightly so. I blame the greedy landlord for being cheap and not sound insulating the room.

There are specialty products out there that absorb noise incredibly well. I cant recall the name, I seen it at a NAEC conference, black rubber almost like a horse stall mat.